The present invention relates to a method for the preparation of an .alpha.-ketoamide imine by the reaction of a halogen-containing organic compound, a primary amine and carbon monoxide in the presence of a carbonylation catalyst.
.alpha.-ketoamide imines include a class of compounds useful as intermediates for the synthesis of various medicines and agricultural chemicals or, in particular, industrially important compounds in the synthetic preparation of amino acids. The starting compounds for the synthetic preparation of the compounds of this class are, in the prior art, usually an .alpha.-keto-acid and a primary amine but this process has not yet been applied to the industrial preparation of amino acids due to the expensiveness of the .alpha.-keto-acids. On the other hand, amino acids are usually prepared either by fermentation or by chemical synthesis. In the latter method of chemical synthesis, one of the most important problems to be solved is in the synthetic route to form the portion ##STR2## in an amino acid ##STR3## in order to establish a generally applicable method for the preparation of amino acids. No generally applicable and economically advantageous method, however, has yet been established for the synthetic preparation of amino acids starting from a halogen-containing organic compound which is usually inexpensive and available in large quantities.
In view of the above mentioned problems in the synthetic preparation of amino acids, the inventors have conducted extensive research and, as a result thereof, have arrived at the discovery of a novel and very interesting reaction, in which one mole of a halogen-containing organic compound reacts in one step with two moles of carbon monoxide in the presence of a primary amine to form an .alpha.-ketoamide imine having a structure expressed by the formula ##STR4## as a precursory structure for the formation of the structure of the formula ##STR5## in the amino acid. The inventors concentrated on this novel reaction which resulted in the completion of the present invention.